You said: “By definition, any calamity is bound to entail evil outcome and consequences, but the Creator of such evil must Himself be evil to have caused it." That is not entirely accurate. Earthquakes are a natural phenomenon but are only calamitous if they damage or destroy property or life. Same can be said of tornados or fierce storms. They are not intrinsically evil or wicked.
Some calamities spoken of in scripture, like the destruction of Sodom and Gomorrah, the Noachian flood, the destruction of Egyptians, Babylonians and such, are calamities to be sure. The Hebrew word is rendered bad, gloomy, evil and calamitous. God brought calamity on Adam and Eve when he carried out the death penalty. He was going to bring calamity upon he Ninevites - those to whom he sent Jonah but they stopped their reprehensible violent behavior so he didn’t.
Governments bring calamity upon rapists, murderers and political traitors in the form of criminal punishment. It is calamitous but it is not wicked or evil for a government to protect its citizens this way, is it?
Calamity or evil is not intrinsically wicked. And so there is no basis for calling God evil simply because he brings calamity upon individuals or groups as punishment for their wanton, callous, illegal behavior.